Gut-vascular barrier mediated Tripterygium wilfordii-induced liver injury: the synergism between triptolide and celastrol via intestinal FXR-ET-1 pathway.

ETHNOPHARMACOLOGICAL RELEVANCE: Therapy based on Tripterygium wilfordii Hook F (TWHF) is considered as one of the most effective and vital treatments for managing rheumatoid arthritis. It induces significant liver toxicities in 11.4 % of the patients, but the mechanisms not well known.

AIM OF THE STUDY: This study examined the mechanisms of the drug interaction between Cela and Trip which mediate the hepatotoxicity of TWHF.

METHODS: Pathological and biochemical methods were utilized to evaluated liver damage. The metabolic alterations occurring in the serum and liver were assessed via metabolism. Transmission electron microscope, Evans blue infiltrating, LPS and DAO activity were used to evaluate GVB. Fxr-knockout mice, intestinal FXR agonists and inhibitors were used to reveal the critical role of intestinal FXR in liver injury. Endothelin-1 (ET-1) inhibitors and over-expression vector were applied to evaluate the regulatory role of FXR-ET-1 in GVB.

RESULTS: The synergistic actions of triptolide (Trip) and celastrol (Cela), two major components in TWHF, led to liver injury, which involved sequential events of FXR inhibition, ET-1 up-regulation, and then GVB disruption. The intestinal FXR inhibition by Cela and probe inhibitor, and FXR knockout significantly aggravated liver injury induced by Trip. Activation of intestinal FXR alleviated liver injury via down-regulating ET-1 and improving GVB integrity. And ET-1 was found to mediate the normal structure and function of GVB. In HUVECs, FXR inhibition by Cela potentiated the ET-1 increase and activation of JNK-Caspase3-GSDME by Trip.

CONCLUSIONS: Thus, Cela as an identified intestinal FXR antagonist up-regulated ET-1 expression, thereby disrupted GVB. This interaction between Cela and Trip mediated TWHF-induced liver injury. Activation of intestinal FXR and protection of GVB were suggested to be strategies for the treatment of DILI.